Multilayered, textile, gas-permeable filter material against toxic chemical substances

ABSTRACT

In order to improve the handling and filtering characteristics of a multilayered, textile, gas-permeable filter material against toxic chemical substances and, in particular, filter and protective materials for the production of sheet-like filters and protective suits for the civil and military fields, it is suggested that this filter material have a first layer as textile support layer which is bonded to a second layer present in the form of an areal adhesive layer. In addition, the filter material has a third layer applied to the second layer and areally bonded thereto, this third layer comprising a textile sheet-like layer containing activated carbon fibers.

BACKGROUND OF THE INVENTION

The invention relates to a multilayered, textile, gas-permeable filtermaterial against toxic chemical substances and, in particular, filterand protective materials for the production of sheet-like filters andprotective suits for the civil and military fields.

Previously known filter materials of the type described at the outsethave a textile support material, on which adsorber beads, in particularactive carbon beads, are adhered via adhesive screens. These beads are,where applicable, protected from any premature wear and tear by agas-permeable protective layer (EP-B 0 090 073).

In addition, filter materials are known, in which a woven fabriccontaining activated carbon fibers is adhered to the textile supportswith an adhesive screen. If such fabrics containing activated carbonfibers are laminated between two textile layers, the material obtainedaccording to EP-A-0 230 097 is merely one, in which the fabriccontaining the activated carbon fibers disintegrates to fine dustalready at the slightest tensile strain.

The disadvantage of the state of the art is that there is insufficientbonding of the textile support material with the activated carbonmaterial and, furthermore, the actual adsorption layer which containsthe activated carbon can only inadequately withstand mechanicalstressing such as that occurring, for example, when protective suitsmade from the protective material are worn.

The object of the invention is to develop the filter material describedin EP-A-230 097, which comprises a first layer as textile support layer,a second layer in the form of an adhesive layer bonded to the firstlayer and a third layer which is applied to the second layer, is bondedthereto and comprises a textile sheet-like layer containing activatedcarbon fibers, further such that the disadvantages specified above areavoided.

SUMMARY OF THE INVENTION

This object is accomplished in accordance with the invention, in thefilter material described at the outset, in that the second layer is anareal adhesive layer consisting of an adhesive spun fiber yarn, fleeceor screen, an adhesive foil, a woven or knitted adhesive fabric or thelike or an open-cell foamed material layer laminated to the adjacentlayer(s) in the flame laminating process and that the second layer isareally bonded to the first and third layers.

This third layer can be additionally protected by a fourth layer in theform of an areal adhesive layer which is applied to the third layer,opposite the second layer, and areally bonded thereto.

Although extremely thin adhesive layers, in particular in the form ofspun yarns, fleeces, foils etc., can be used for the adhesive layers,the fourth layer as adhesive layer is, in particular, sufficient toadditionally stabilize the third layer with the textile sheet-like layercontaining the activated carbon and to protect it against wear and tear.Surprisingly, the fourth layer offers not only an adequate, mechanicalprotective effect against wear and tear but also leads, in addition andin cooperation with the second layer in the form of an areal adhesivelayer, to a strengthening of the third layer held between the two layersso that this can, for the most part, be selected wholly in view of itsprotective effect, independently of its inherent mechanical stability,and used in the protective material.

A particularly suitable adhesive layer material is available in the formof slotted adhesive coating foils which act as a type of dry meltingadhesive.

The adhesive layer material is preferably produced from a thermoplasticpolymer material, reference being made in this respect, in particular,to the plastic materials PVC, polyurethane, polyester and polyamide. Itis important in the case of the adhesive layers for them to beadequately gas-permeable, i.e. that the foils have, in particular, aperforation, preferably a microperforation, which is retained during thethermal bonding or the thermal activation of the adhesive layer duringprocessing.

Apart from the adhesive layer materials described in the above, anopen-cell foamed material layer which is laminated on is particularlysuitable and this, due to its foam structure, takes over not only thefunction of an adhesive but also, simultaneously, the function of aprotective layer against mechanical damage to the textile sheet-likelayer containing activated carbon fibers. A flame laminating method ispreferably used for the lamination process, whereby the thickness of thelayer remaining in the finished product--and therefore the protectiveeffect of the foamed material layer--can be predetermined very exactly.The thickness of the foamed material layer can be selected such that theareal filter material is permanently deformable in a subsequenttreatment step using heat and pressure.

Moreover, reticulated foamed materials are suitable as adhesive layermaterials; these exercise not only the function of an adhesive but alsoa filtering function, above all in contact with liquids. A mechanicalprotective effect is also offered by the reticulated foamed materials.

In the case of protective materials, reticulated foamed material ispreferably used on the external side as adhesive layer while open-cellfoamed material is preferably used on the inner side, i.e. the sidefacing the skin.

For the first time it is now suggested to use the flame laminatingprocess during the production of textiles which are used in theproduction of clothing.

The textile sheet-like layer which contains the activated carbon fiberscan, in principle, be manufactured according to different technologies,for example according to the teaching of EP 0 079 488 B1, EP 0 230 097A2 or also DE 33 25 644 C2.

These technologies deal with woven fabrics which comprise activatedcarbon staple fibers, whereby the first-named EP 0 079 488 discloseswoven fabrics made from a composite yarn of textile staple fiberscontaining a proportion of active carbon staple fibers which is between5 and 75% by weight. The proportion of staple fibers which does notconsist of active carbon staple fibers is essentially responsible forthe stability of the composite yarn or the woven fabric formedtherefrom.

Alternatively, a process according to EP 0 230 097 A2 is conceivable,where activated carbon fibers are needled to an additional textilematerial and thereby form a type of areal felt-like layer.

The third type differing herefrom is formed by DE 33 25 644 C2 where aspun yarn made from activated carbon fibers is used.

The greatest adsorption activity is to be expected from the last-namedtype of fiber or textile sheet-like layer material, whereby it is,however, to be pointed out at the same time that the mechanical strengthof this type of adsorber layer is less in comparison with the other twotypes.

This textile sheet-like layer with the activated carbon fibers can beprovided as woven fabric, felt, knitted fabric, fleece etc. As alreadyspecified in the above, it is not necessary due to the inventivestructure for the textile sheet-like layer with the activated carbonfibers to have a particular mechanical strength since this is given toit by the adhesive layers covering it areally, where applicable, on bothsides.

The three, four or more layers are brought together during production toform a pile and pass as a stacked layer through a heating zone which ispreferably formed by heating rollers. In the heating zone, the adhesiveof the second and fourth (when present) layers is activated and thusprovides for an areal bonding of the pile.

During the flame lamination of the foamed material layers, the textilesupport layer is first of all laminated with a foamed material layerand, subsequently, the textile sheet-like layer containing activatedcarbon fibers is laminated onto this double layer in an additionallaminating process on the side of the free foamed material layer.Alternatively, the three layers, namely the textile support layer, thefoamed material layer and the sheet-like layer, can also be processedtogether and brought together simultaneously in one method step, wherebythe two laminating processes then run at the same time.

Depending on the conditions selected for the flame lamination, thethickness of the foamed material layer can be reduced as required duringa lamination process and therefore adapted to the intended use of thefinished filter material in many respects, for example with regard tothe thermal passage value, air permeability, protective effect againstmechanical influences etc.

Finally, in a preferred embodiment, a fifth layer can be provided in theform of a microporous, gas-permeable but liquid-impermeable material asadditional protective layer. This can rest essentially loosely on thepile of layers one to four or, however, be areally bonded to the fourthlayer.

The textile support layer (first layer) is preferably produced from anair-permeable, tear-resistant and dimensionally stable material. Thetextile support layer can therefore define the mechanical properties forthe filter material as a whole, in particular tensile strength andelongation strength, whereby, in particular, the dimensional stabilityof the material and a correspondingly smaller value for the elasticelongation of the material ensure that the textile sheet-like layercontaining activated carbon fibers which is to be protected is notstretched beyond the allowable degree during use of the filtermaterials.

In view of these desired properties, the textile support layerpreferably has a tensile strength of>300N. With regard to the elasticelongation, it is desirable for the textile support layer to have avalue of<12%. The conventional materials available for producing thetextile sheet-like layer containing activated carbon fibers easilysustain an elastic elongation of<12%. Thereafter, the elasticextensibility of the textile support layer has a limiting effect for thefurther elongation and thus prevents any tearing of the textilesheet-like layer containing activated carbon fibers within the filtermaterial.

The textile support layer, the essential task of which is first to lendthe filter material a dimensional stability and a certain tensilestrength, can be selected with a very low weight per unit area of, forexample, 30 g/m² to 150 g/m² so that it contributes little to the weightper unit area of the filter material but, on the other hand, fulfillsthe functions defined above in full.

The gas permeability of the textile support layer, insofar as this is ofsignificance only in its support function for the filter material,should preferably be between 100 to 500 l/(dm² ×min).

If the filter material is intended to be used as protective material inprotective clothing, there are cases of use where the textile supportlayer is preferably produced from a woven microfiber fabric which is,indeed, gas-permeable but protects against strain due to wind. In thiscase, the gas permeability is then essentially less than previouslydefined, namely approximately 10 to 30 l/(dm² ×min). Then, the supportlayer preferably has, at the same time, the advantage of waterimpermeability, namely up to a column of water of at least 500 mm,preferably at least 1000 mm. The support layer can, in this case,function simultaneously as upper layer or cover layer.

The woven microfiber fabric prevents liquid penetrating as far as thesheet-like layer containing activated carbon fibers, wetting theactivated carbon fibers and thereby reducing the absorptive capacity andfiltering effect for harmful gases.

The foamed material layer in the finished filter material preferably hasa thickness of up to 0.7 mm, in addition preferably in the range ofapproximately 0.3 mm to approximately 0.5 mm.

The thermal insulation value of the three-layered filter material is, inparticular when the filter material is used as protective material forprotective clothing, preferably≦70×10³ m² K/W. The third layer, which isformed from the textile sheet-like layer containing activated carbonfibers, can be provided with a fourth layer in the form of an open-cellfoamed material layer as additional layer improving the strengths of thefilter material and, in particular, the mechanical serviceability of thesheet-like layer; this fourth layer is then preferably laminated onlikewise by flame lamination. A preferable effect in this case is thefact that the second foamed material layer is laminated on together witha second textile layer so that, in the end, a six-layered laminatedmaterial is obtained. The duplicated textile layers and foamed materiallayers can either be the same as one another or different from oneanother, depending on the purpose for which the filter material is used.

The foamed material layers can, in particular, have a differentthickness, depending on whether they come to be located on the inside orthe outside, for example, in a protective material for protectiveclothing.

In a preferred embodiment of the invention, the first and/or the secondfoamed material layer is heat-deformable and following the heat-formingstep forms an essentially self-supporting structure for the filtermaterial. This can be used for the production of, for example, filtermaterials having a large surface area and a zigzag structure in thesectional view or filter materials having a certain shape can be formedwhich make the filter material suitable as a complete filter element infilter devices.

In the following, the invention will be explained in greater detail onthe basis of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a four-layered, inventive filter material;

FIG. 1a is a diagram showing the process sequence relating to the filtermaterial of FIG. 1;

FIG. 2 shows a six-layered, inventive filter material;

FIG. 2a is a diagram showing the process sequence relating to the filtermaterial of FIG. 2;

FIG. 3 shows a five-layered, inventive filter material; and

FIGS. 3a and 3b are diagrams showing the process sequence relating tothe filter material of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an inventive, multilayered, textile filter material whichcan be used as protective material in protective clothing, whereby afirst, textile layer as support layer is designated with the referencenumeral 1, a second layer in the form of an areal adhesive layer whichis areally bonded to the first layer is designated with the referencenumeral 2, a third layer which is applied to the second layer andareally bonded thereto and comprises a textile sheet-like layercontaining activated carbon fibers is designated with the referencenumeral 3 and a fourth layer which, like the second layer 2, representsan areal adhesive layer which is applied to the third layer opposite thesecond and is areally bonded thereto is designated with the referencenumeral 4.

Preferably, the support layer 1 has a weave structure while the adhesivelayers 2 and 4 are either produced from a relatively dense adhesive spunfiber yarn, fleece or woven fabric or the like but are gas-permeable orthey are provided in the form of a foil which has a perforation whichessentially remains even after the adhesive process. The third layer 3is formed by an adsorption layer which consists of a woven fabricproduced from a spun yarn made from activated carbon fibers, asdescribed in DE 33 25 644 C2.

The fourth layer 4 functioning as a cover layer is again formed by a PUadhesive fleece or adhesive foil and can consist of the same material asthe second layer.

Suitable foils are, in particular, also those foils which havepunctiform material concentrations in a regular distribution.

The support layer 1, predominantly a woven, weft-knit or knitted fabric,having a weight per unit area of 50 to 1000 g/m², preferably 100 to 400g/m², is intended to have an air permeability of 10 to 1000 l/min×100cm², mainly, however, of 100 to 400 l/min×100 cm², measured at 1 mbarunderpressure.

The adsorption layer 3 can either be produced from spun yarns which canconsist of activated carbon fibers or of filament yarns which can,again, consist of activated carbons, or the adsorption layer 3 isactivated in a second operational step in a water vapor atmosphere at800° C.

The adsorption layer 3 can equally be formed from spun fiber yarnconsisting of carbonaceous materials, in particular on the basis ofpreoxidized polyacrylonitrile, either to 100% or in a mixture withanother spun fiber of comparable length. The composite yarn resultingtherefrom consists to 10 to 90% by weight of carbonaceous fibermaterial, mainly 30 to 70% by weight, and for the rest of textile spunfibers, in particular of natural fibers or chemical fibers, which canagain consist of natural polymers on an organic or inorganic basis or ofsynthetic materials, in particular cotton, wool, silk, polyamide,polyester, polyacryl, aramide or viscose fibers. From a statisticalpoint of view, the spun fibers are present in the yarn core in an evendistribution. Either flame-retardant substances can be added to thesefibers or they can be impregnated in a flame-retardant manner in anadditional finishing process. These fibers preferably have a fineness inthe range of 0.4 to 7 dtex, mainly 0.8 to 2 dtex, and a staple length of10 to 100 mm, mainly of 30 to 60 mm. These fibers can be either smoothor crimped.

Either the fiber is activated or the yarn or a finished textile fabric.The specific surface area of the adsorption layer 3 should be from 100to 2000 m² /g, preferably 800 to 1200 m² /g.

The yarns spun from these materials can be produced either according toclassic spinning methods, such as, for example, the ring spinningmethod, or according to newer spinning methods, such as open-end rotorspinning, open-end friction spinning, twist spinning, rubbing(self-twist), respooling method, false-twist method,bonding/heat-sealing or felting.

FIG. 1a shows on the basis of a block diagram a preferred processsequence for producing the filter material shown in FIG. 1. In thisrespect, the individual four layers 1, 2, 3 and 4 are first broughttogether and fed to the device for adhesive lamination as a four-layeredpile. The result is the multilayered, stacked material 1/2/3/4 areallybonded together.

FIGS. 2 and 3 show filter materials which comprise a combination ofthree layers as a basic structure, namely a support or cover layer, asoft foam layer and a sheet-like layer containing active carbon fibers.This basic structure is varied in FIGS. 2 and 3 for two differentapplications, as will be described in the following.

FIG. 2 illustrates a six-layered structure of a filter material whichcomprises a support layer 1a which can be produced, for example, from aknitted polyester material (warp knit fabric) and in the present casehas a weight per unit area of approximately 40 g/m². This is followed bya membrane 2a as second layer on the basis of hydrophilic polyurethanewhich is applied to the support layer 1a by means of reverse coatingwith a weight per unit area of approximately 40 g/m². Impraperm of thecompany Bayer AG is preferably used for this. This membrane 2a isliquid-tight up to and above 700 mm of water column.

A foamed material layer 3a is applied as third layer in the flamelaminating process and this can be formed from polyurethane, a softpolyurethane ether foam or a soft polyurethane ester foam. In this case,a material having a bulk density of 42 kg/m³ is preferably used. Thecompression hardness of this material is 4.9 kPa, the number of cellsper cm 17±3. The thickness of the starting material is, in this example,1.6 mm, the thickness in the finished product 0.3 mm. The third layer ispreferably finished in a flame-retardant manner.

A sheet-like layer 4a consisting of a completely carbonized andactivated woven viscose fabric is used as fourth layer, in this examplewith a weight per unit area of 120 g/², a thickness of 0.45 mm and aspecific inner surface area of 1000 to 1200 m² /g.

An adhesive layer 5a in the form of a hydrophilic adhesive coating(polyurethane basis) is laminated as fifth layer to the sheet-like layer4a, namely with a weight per unit area of approximately 8 g/m². A wovenface fabric is applied as last layer in the form of a cover layer 6a andthis can, of course, also be replaced by a weft-knit or knitted textilelayer. In the present example, a twill cloth is used (65% viscose, 35%Nomex) with a weight per unit area of approximately 260 g/m².

By incorporating a suitable membrane in the structure of the filtermaterial, the protective properties of a protective clothing system madefrom the material as described can be considerably improved in relationto toxic chemical substances whilst ensuring an adequate water vaporpermeability and so it is also possible to use such systems for purposeswhich could not be covered with permeable protective clothing systemspreviously known and which had therefore to be accomplished solely withinsulating (e.g. rubberized) protective suits. Due to the water vaporpermeability of the membrane, the physiological wearing properties canbe noticeably improved in comparison with insulating protective clothingsystems and therefore longer wearing times can be achieved. By using thematerial structure as described, such protective clothing systems can,for example, be used, in particular, for ABC defence personnel (ofdetection, decontamination units, etc.) in the armed forces and in civildefence as well as for combat clothing for ship's crews in the navalforces (battle dress sea with integrated ABC protection).

The flame laminating process which is used according to the presentinvention for the first time in the production of protective materialsfor the production of clothing is of particular significance for thelamination of the foamed material layers. The use of foamed materiallayers as adhesive layers is preferred on account of the advantagesdescribed in the above, which are particularly effective in conjunctionwith the flame laminating process.

FIG. 2a shows a preferred production process for the product shown inFIG. 2 in the form of a block diagram.

First of all, a membrane 2a made of hydrophilic polyurethane is appliedto the support layer 1a with a reverse coating process.

This modified support layer 1a/2a is brought together with the foamedmaterial layer 3a and the sheet-like layer 4a made of carbonized wovenviscose fabric in a process step and they are bonded to one another in acommon flame lamination step. The multilayered material 1a/2a/3a/4a thusobtained is provided with a hydrophilic adhesive coating 5a and broughttogether with the cover layer 6a and areally bonded in an adhesivelamination step to form the product 1a/2a/3a/4a/5a/6a.

FIG. 3 shows a different type of structure, in which a soft polyurethanefoam layer 2b (on the basis of polyurethane ethers or polyurethaneesters) is applied to a support layer 1b which can be a woven, knitted,weft-knit fabric etc. A sheet-like layer 3b which contains active carbonfibers is applied to this double layer. A PU soft foam layer 4b can,again, be laminated to this three-layered material and following thisfoam layer a cover layer 5b, or the layers 4b and 5b are already bondedto one another beforehand in a laminating process and then laminated tothe threefold layer consisting of the layers 1b, 2b and 3b as a doublelayer.

The material structure thus created ensures the required high protectivecapacity of the protective clothing system with respect to toxicchemical substances with, at the same time, additional, considerableimprovement in the microclimate underneath the protective suit. Onaccount of the considerably more favorable physiological wearingproperties which are thus achieved the material is suitable, inparticular, for protective clothing systems which can be used

as required, as protective suits to be worn over normal uniforms("overgarment"),

as army combat suits with integrated ABC protection for climatically hotregions or

as protective clothing in civil defence and protection of the civilianpopulation or the like.

Due to the possibilities for varying the individual material layers,both universally usable protective clothing systems as well as clothingsystems complying with specific customer requirements can be coveredwithin the scope of the material structure described.

The processes described in the above are shown in a summarized manner inthe form of block diagrams in FIGS. 3a and 3b.

According to the process shown in FIG. 3a, the support layer 1bconsisting of a linen fabric (65% viscose, 35% Nomex) and having aweight per unit area of approximately 150 g/m² is first of all areallybonded to the open-cell foamed material laminating layer 2b(polyurethane ether type) having a bulk density of 42 kg/m³, acompression hardness of 4.9 kPa, 17±3 cells per cm, a material thicknessof 1.6 mm and a thickness in the finished product of 0.3 mm in a flamelamination step.

The flame-laminated support layer 1b/2b is brought together in thefollowing step with the sheet-like layer 3b (100% activated carbonfibers) having a weight per unit area of approximately 120 g/m², athickness of 0.45 mm and an inner specific surface area of 1000-1200 m²and flame laminated.

The threefold layer 1b/2b/3b is given on the side of the sheet-likelayer 3b an adhesive coating 4b consisting of hydrophilic polyurethanehaving a weight per unit area of approximately 8 g/m² and is thenbrought together with the cover layer 5b. The cover layer preferablyconsists of non-woven material (Sontara spun fleece) made fromNomex/Kevlar having a weight per unit area of approximately 31 g/m².These superimposed layers are areally bonded to one another in a finaladhesive lamination step to form the end product 1b/2b/3b/4b/5b.

Alternatively, the layers 4b and 5b can be brought together according tothe process sequence shown in FIG. 3b and bonded in a flame laminationstep. The material of the layer 4b is in this case a flame-laminatablefoamed material, such as that already used for the layer 2b.Subsequently, the threefold layer 1b/2b/3b (cf. FIG. 3a) is bonded tothe double layer 4b/5b in a fourth flame lamination step to form theproduct 1b/2b/3b/4b/5b.

What is claimed is:
 1. A multilayered, textile, gas-permeable materialfor filtering against toxic chemical substances, comprising:a firstlayer as a textile support layer; a second layer in the form of anadhesive layer bonded to said first layer; a third layer applied to saidsecond layer and bonded thereto, said third layer comprising a textilesheet-like layer containing activated carbon fibers; and a fourth layerserving as a protective layer for said third layer in the form of anadhesive layer, arranged opposite the second layer and unilaterallybonded to the third layer wherein the second layer is an areal adhesivelayer, said second layer being areally bonded to the first and thirdlayers.
 2. A filter material as defined in claim 1, wherein the secondand the fourth layer is selected from the group consisting of at leastone of an adhesive spun fiber yarn, fleece or screen, an adhesive foil,a woven or knitted adhesive fabric or an open-cell foamed material layerlaminated to the adjacent layer(s) by a flame laminating process.
 3. Afilter material as defined in claim 2, wherein the adhesive layermaterial is a thermoplastic polymer material selected from the groupconsisting of at least one of polyurethane, polyvinyl chloride,polyamide and polyester.
 4. A filter material as defined in claim 1,wherein the second and fourth layers are open-cell foamed materiallayers laminated to the adjacent layer by a flame laminating process. 5.A filter material as defined in claim 1, wherein the textile sheet-likelayer comprises the activated carbon fibers in a mixture with staplefibers processed to form a composite yarn.
 6. A filter material asdefined in claim 1, wherein the textile sheet-like layer essentiallyconsists exclusively of activated carbon fibers.
 7. A filter material asdefined in claim 1, wherein the textile sheet-like layer is selectedfrom the group consisting of a woven, a felt, a weft-knit, a knitted anda fleece structure.
 8. A filter material as defined in claim 1, furthercomprising a fifth layer in the form of a microporous, gas-permeable butliquid-impermeable material adjacent to the fourth layer.
 9. A filtermaterial as defined in claim 1, further comprising a fifth layer in theform of a membrane based on a hydrophilic polyurethane polymer, saidfifth layer being arranged adjacent to the fourth layer.
 10. A filtermaterial as defined in claim 1, wherein the textile support layer isproduced from an air-permeable, tear-resistant and dimensionally stablematerial.
 11. A filter material as defined in claim 10, wherein thetextile support layer has a tensile strength of>300N.
 12. A filtermaterial as defined in claim 10, wherein the textile support layer hasan elastic elongation of<12%.
 13. A filter material as defined in claim10, wherein the textile support layer has a weight per unit area ofapproximately 30 g/m² to 150 g/m².
 14. A filter material as defined inclaim 10, wherein the gas permeability of the textile support layer iswithin a range from about 100 to 500 1/(dm² ×min).
 15. A filter materialas defined in claim 1, wherein the textile support layer is a wovenmicrofiber fabric.
 16. A filter material as defined in claim 15, whereinthe gas permeability of the textile support layer is approximately 10 to30 l/(dm² ×min) and the support layer is watertight up to a column ofwater of at least approximately 500 mm.
 17. A filter material as definedin claim 4, wherein the foamed material layer in the finished filtermaterial has a thickness of approximately 0.3 mm to approximately 0.5mm.
 18. A filter material as defined in claim 1, wherein the thermalinsulation value of the first, second and third layers of the filtermaterial is together≦70×10³ m² K/W.
 19. A filter material as defined inclaim 4, wherein said fourth layer is laminated to the third layer inthe form of a second open-cell foamed material layer.
 20. A filtermaterial as defined in claim 19, wherein the second foamed materiallayer is laminated together with a second textile layer.
 21. A filtermaterial as defined in claim 19, wherein at least one of the first andthe second foamed material layers is heat-deformable and forms aself-supporting structure of the filter material.
 22. A filter for thesupply of fresh air in motor vehicles constructed from the filtermaterial of claim
 1. 23. A protective suit, constructed from the filtermaterial of claim
 1. 24. A filter element for ventilation systems ofmotor vehicles, produced with the use of the filter material of claim 1.25. A filter element as defined in claim 24, wherein the filter materialis formed in a thermoforming step.
 26. A filter element as defined inclaim 25, wherein the filter material is designed as a self-supportingcomponent.
 27. A filter element as defined in claim 26, wherein thefilter material is designed with one of a rib or corrugated structurefor improving its inherent stability.
 28. Shoe insoles, produced from afilter material as defined in claim
 1. 29. A filter material as definedin claim 1, wherein said second layer is applied over substantially theentire first layer.
 30. A filter material as defined in claim 1, whereinsaid third layer is applied over substantially the entire second layer.31. A filter material as defined in claim 1, wherein said fourth layeris applied over substantially the entire third layer.
 32. A filtermaterial as defined in claim 1, wherein said fourth layer is an outerlayer of said material.
 33. A filter material as defined in claim 9,wherein said fifth layer passes water vapor at a rate of approximately200 g/(m² ×24 h).
 34. A filter material as defined in claim 16, whereinsaid support layer is watertight up to a column of water of at leastapproximately 1,000 mm.